TEHRAN (FNA)- Researchers succeeded in an experiment where they get
an artificial atom to survive ten times longer than normal by
positioning the atom in front of a mirror.

If one adds energy to an atom -- one says that the atom is excited
-- it normally takes some time before the atom loses energy and returns
to its original state. This time is called the lifetime of the atom.
Researchers at Chalmers University of Technology have placed an
artificial atom at a specific distance in front of a short circuit that
acts as a mirror. By changing the distance to the mirror, they can get
the atom to live longer, up to ten times as long as if the mirror had
not been there.

The artificial atom is actually a superconducting electrical
circuit that the researchers make behave as an atom. Just like a natural
atom, you can charge it with energy; excite the atom; which it then
emits in the form of light particles. In this case, the light has a much
lower frequency than ordinary light and in reality is microwaves.

"We have demonstrated how we can control the lifetime of an
atom in a very simple way," says Per Delsing, Professor of Physics
and leader of the research team. "We can vary the lifetime of the
atom by changing the distance between the atom and the mirror. If we
place the atom at a certain distance from the mirror the atom's
lifetime is extended by such a length that we are not even able to
observe the atom. Consequently, we can hide the atom in front of a
mirror," he continues.

The experiment is a collaboration between experimental and
theoretical physicists at Chalmers, the latter have developed the theory
for how the atom's lifetime varies depending on the distance to the
mirror.

"The reason why the atom "dies," that is it returns
to its original ground state, is that it sees the very small variations
in the electromagnetic field which must exist due to quantum theory,
known as vacuum fluctuations," says GE[micro]ran Johansson,
Professor of Theoretical and Applied Quantum Physics and leader of the
theory group.

When the atom is placed in front of the mirror it interacts with
its mirror image, which changes the amount of vacuum fluctuations to
which the atom is exposed. The system that the Chalmers researchers
succeeded in building is particularly well suited for measuring the
vacuum fluctuations, which otherwise is a very difficult thing to
measure.

The findings are published in the highly ranked Nature Physics
journal.

Facts about the research:

The sample that the researchers used is fabricated on a silicon
chip and contains two key elements. The first is a superconducting
circuit forming the artificial atom. The second part is a short circuit
that acts as a mirror. By sending a very weak signal to the atom,
researchers can measure its lifetime. At the same time, they can vary
the effective distance to the mirror. This is done by changing the
atomic resonance frequency, while the actual distance remains constant.
By doing this you can control the distance measured in the number of
wavelengths of light/microwaves. A frequency of 4.8 GHz was used in the
experiment, which is close to the radio waves used in wireless networks.
The experiments were performed at very low temperatures, close to
absolute zero (30 mK) to ensure the atom is in its ground state at the
start of the experiment.